The nuclear factor kappa beta (NF-kB), a redox-sensitive transcription factor, is well established as a regulator of genes coding for both proapoptosis and prosurvival proteins. It has been shown that hormone-independent prostate cancer has a high constitutive level of NF-kB and activation of NF-kB by cancer therapeutic agents can blunt the activity of these agents to cause cancer cell death. The goal of this project is to gain insight into an NF-kB mediated mechanism leading to intrinsic radiation resistance and to identify novel approaches that can be used to improve the treatment of prostate cancer. Our initial data demonstrate that androgen-independent prostate cancer has high levels of selected members of the NF-kB family and its prosurvival NF-kB target gene products including the primary antioxidant enzyme, manganese superoxide dismutase, and the antiapoptotic protein, BclXL. We also found that radiation induced activation of NF-kB in a two-wave pattern. We hypothesize that tumor cells with high levels of constitutive NF-kB will be sensitive to inhibition of the NF-kB mediated cytoprotective pathway and modulation of this pathway can improve the radiation response of aggressive prostate cancer. Parental PC-3 and its NF-kB mutant derived cell lines will be used as models for androgen-independent prostate cancer cells. Parental LNCaP and its corresponding derivatives will be used as models for androgen-dependent prostate cancer cells. Well characterized PC-3 derived as well as LNCaP derived prostate cancer cell lines will be studied in vitro and in vivo. Five-weeks-old male athymic nude mice will be used as hosts of human prostate cancer cells by orthotopic implantation in the prostate glands. Specific aim 1 is designed to identify specific members of the NF-kB family that play an important role in high intrinsic radioresistance of aggressive prostate cancer cells. Specific aim 2 is designed to test the concept that selective modulation of NF-kB or redox-based intervention can be used to enhance radiation sensitivity. Specific aim 3 is designed to validate the results from Specific aim 2 in an experimental therapeutic setting. Accomplishment of this study will enhance our understanding of the mechanisms by which members of the NF-kB family participate in cell survival. This information can serve as a rationale for the development of selective approaches that might eventually translate into significant clinical benefit.